1. Technical Field
A solution for ruthenium chemical mechanical planarization (abbreviated as xe2x80x9cCMPxe2x80x9d) containing a nitric acid and an oxidizer is disclosed. In particular, the forming method of a ruthenium pattern including CMP process using the above solution for ruthenium CMP is disclosed.
2. Description of the Related Art
Ruthenium is a noble metal which is chemically and mechanically stable, and is an essential material used in fabricating high performance semiconductor devices. In addition, ruthenium has been recently used as lower electrode in forming metal layer/insulating film/metal layer-type capacitors in DRAM devices.
However, an appropriate CMP slurry cannot be provided to polish the ruthenium during a CMP process because ruthenium has relatively low reactivity. Thus, the slurries intended for other metals such as tungsten or aluminum are employed when polishing ruthenium.
The slurries intended for other metals include chemicals for planarizing of the various metal layers on a silicon substrate. In general, the slurry for a metal CMP process with a strong acidity of pH 2xcx9c4 contains an oxidizer such as hydrogen peroxide (H2O2) or ferric nitrate (Fe(NO3)2) and an abrasive such as alumina (Al2O3) or manganese oxide (MnO2). Further, a small amount of surfactant may be added to improve CMP slurry properties.
The polishing speed of ruthenium is very slow, thus the CMP process is performed for a long period of time under a high polishing pressure in order to adequately planarize the ruthenium.
As a result, the ruthenium layer may be separated from the interlayer insulating film because the ruthenium layer has poor adhesion to the interlayer insulating film. In addition, dishing and erosion effects are generated on the ruthenium layer adjacent to the interlayer insulating film.
Moreover, when ruthenium is polished for a long time under high polishing pressure, the abrasive in the slurry can scratch the interlayer insulating film severely, and impurities such as the slurry grounds are generated and remain behind. Therefore, the property of the resultant device is deteriorated.
A solution for ruthenium CMP is disclosed which can improve the polishing speed of ruthenium under a low polishing pressure and reduce dishing of ruthenium layer and scratches of the interlayer insulating film.
A method for forming a metal pattern including CMP process using the above solution is also disclosed.